Nitro-stilbene-hydroxyalkyl sulfones and process of preparing same



United States Patent 3,086,057 NITRO-STILBENE-HYDROXYALKYL SULFONES ANDPROCESS OF PREPARING SAME Asim Kumar Sarkar, Leeds, England, assignor toHickson & Welch Limited, Castleford, England, a British com- P NoDrawing. Filed May 3, 1961, Ser. No. 107,305 Claims priority,application Great Britain May 4, 1960 12 Claims. (Cl. 260-607) Thisinvention is concerned with new chemical compounds of use inter alia asintermediates in the production of stilbyl group-containing opticalwhitening agents.

Certain stilbyl group-containing optical whitening agents, for examplestilbyl triazoles, ate conveniently prepared by a process whichcomprises the steps of condensing an aromatic monoor di-aldehydeiwith aderivative of a 4- nitro-tolueneQ-sulphonic acid, reducing the nitrogroup of the resulting compound to an amino group, diazotizing theresultant amino compound and coupling the diazotized compound with anamino group-containing cyclic compound in a position ortho to said aminogroup, oxidation of the resultant amino group yielding a triazolecompound.

As described in British patent specification No. 668,199 attempts tocondense aromatic aldehydes with nitrotoluene sulphonic acids or certainderivatives thereof give rise to difiiculties, and the production ofsuitable stilbene deriva-tives for use in the synthesis of opticalwhitening agents is achieved according to that specification bycondensation of an appropriate aromatic aldehyde with a nitrotoluenesulphonic acid aryl ester.

In efforts to produce optical whitening agents having balancedsolubility or dispersibility it was attempted to make compounds of thestilbyl triazole type containing in place of the sulphonic acid group orgroups (attached to the stilbene nucleus) one or more sulphone groupwhich latter have a hydrophilic group. For this purpose the condensationof aromatic aldehydes with various nitrotoluene sulphones containinghydrophilic groups in the sulphone residue was investigated but it wasfound in many cases that this reaction is unsatisfactory. For examplethe reaction of a carboxyalkyl sulphone derivative of nitrotoluene witharomatic aldehydes proceeds with difliculty. It was found however thatthe condensation of aromatic aldehydes with hydroxyalkyl or hydroxypolyoxyalkylene sulphone derivatives of nitrotoluene proceeds in generaleconomically and enables the corresponding stilbyl sulphone derivativesto be readily obtained. By this means therefore it is possible toproduce readily new and useful intermediates for the synthesis ofstilbyl optical Whitening agents containing a sulphone group or groupshaving a hydrophilic group therein. Such optical whitening agents havebeen found to have useful properties and are the subject of copending U.8. application No. 107,304, filed May 3, 1961.

According to the invention therefore there is provided a process for theproduction of stilbyl sulphones useful inter alia as intermediates inthe production of optical whitening agents and dyestuffs which comprisescondensing an aromatic aldehyde with a nitrotoluene substituted by agroup SO -(RO),,R" in which R is an alkylene or a hydroxyalkylene group,R" is a hydrogen atom or an alkyl group and n is an integer; thealkylene group in said group SO (RO) R" preferably containing at leasttwo carbon atoms.

Suitable nitrotoluene sulphones for use as starting materials for theprocess of the invention have the general 3,086,057 Patented Apr. 16,1963 where X is R being an alkyl group containing 1 to 4 carbon atoms.

The invention further provides new stilbyl derivatives useful asintermediates for the preparation of optical whitening agents anddyestuffs and having the general formula amnion-gm)...

X in which Rt represents an aromatic residue andX and X have themeanings stated above, and m is either 1 or 2.

These componds, which are new compounds, can themselves be converted tocompounds useful as optical whitening agents (see U.S. application No.107,304) by a process for example including reduction of the nitro groupX or X diazotization of the resulting amino compound, coupling of saiddiazotized product with an amino-substituted heterocyclic or aromaticcompound capable of coupling therewith in a position ortho to said aminogroup, the resultant o-amino azo dye then being oxidised to give atriazole useful as an optical whitening agent.

The nitrotoluene sulphones used in the process according to theinvention can be prepared in any convenient manner. The compounds ofFormula I are particularly readily prepared by reaction of the parentsulphinic acid or a salt thereof, in particular an alkali-metal salt,with one or more molecules of an appropriate alkylene oxide in which thealkylene group contains at least two carbon atoms; examples ofparticularly suitable oxides include those oxides the alkylene groups ofwhich contain 2-6 carbon atoms, in particular ethylene and propyleneoxide. The compounds of general Formula I may also be prepared by thereaction of the parent sulphinic acid or a salt thereof, in particularalkali-metal salt, with an alkylene halohydrin, the alkylene group ofwhich contains at least two carbon atoms. Preferred halohydrins arethose the alkylene groups of which contain 2-6 carbon atoms, inparticular ethylene chlorohydrin and propylene chlorohydrin.

The reaction of the alkylene oxide or of the halohydrin with the parentsulphinic acid (that is with 4-nitrotoluene-Z-sulphinic acid or2-nitrotoluene-4-sulphinic acid) or a salt thereof may be carried outunder various conditions. Thus in the case of ethylene oxide one mayeifect the reaction at slightly elevated temperature, the pH beingcontrolled during the reaction at about 7-8, either by addition of acidor by buifering the reaction mixture. Similar conditions may, ingeneral, be used for the reaction of the other alkylene oxides andhalohydrins.

The condensation of the nitrotoluene sulphone with the aromatic aldehydeis preferably effected in the presence of a basic catalyst. Suitablecatalysts include in particular secondary amines such as piperidine,morpholine and dibutylamine, of which piperidine is generally to bepreferred. The reaction is convieniently efiected at an elevatedtemperature for example oil bath temperature and may if desired bycarried out in a high boiling inert organic solvent.

As examples of aromatic aldehydes which may be used in accordance withthe invention may be mentioned aromatic monoaldehydes in which thealdehyde group is a ring substituent such as benzaldehyde, andnuclearsubstituted derivatives of such aldehydes, not containingsubstituents reactive with aldehyde groups, as well as naphthaldehydesand dialdehydes such as terephthalaldehyde and isophthalaldehyde whichmay also be substituted in the nucleus by substituents which are notreactive to aldehyde groups.

In order that the invention may be more fully understood, the followingexamples are given, by way of illustration only. In these examples partsare by weight.

EXAMPLE 1 16.5 parts of 4-nitro-toluene-2-(hydroxyethyl)-sulphone, 2parts of piperidine and 10 parts of benzaldehyde are heated to 140 C.(oil bath temperature), for 6 hours. At the end of 6 hours the reactionmixture is slurried in glacial acetic acid and filtered. A yellow solid(18 g.) M.P. 13940 of 4-nitro-stilbene-2-(ii-hydroxyethyl) sulphone isobtained. The solid can be recrystallised from acetic acid.

The starting sulphone used in this example may be prepared by either ofthe following methods.

Method 1 60 gms. sodium-4-nitro-toluene-2-sulphinate (80%) are refluxedwith 200 gms. of ethylene chlorohydrin for hours. Excess ethylenechlorohydrin is then distilled off and crystallisation of the crudesolid so obtained from chloroform gives 10.5 gms. of pure4-nitro-toluene-2(;3- hydroxyethyl)-sulphone. M.P. l38140 C.

Method 2 23.5 gms. of 4-nitro-to1uene-2-su1phinic acid are sus pended in200 ccs. of Water. The suspension is neutralised with a solution ofsodium hydroxide. The solution at this stage should be alkaline toBrilliant Yellow. 8.4 gms. of boric acid are added to the solution. 12.5gms. of ethylene oxide are now added below C. to the solution, and thetemperature of the solution raised to 60 C. under stirring. At the endof 1 hour a further 12.5 gms. of ethylene oxide are added and again thetemperature is raised to 60 C. This procedure is repeated till a totalof 70 gms. of ethylene oxide has been added. 4-nitro-toluene-2(,Bhydroxyethyl) sulphone crystallised out at the end of the reaction. Thesuspension is filtered to give 24 gms. of the compound. M.P. 137139 C.

EXAMPLE 2 43 gms. of 4-nitro-toluene-Z-sulphinic acid are suspended in400 ccs. of water. The suspension is neutralised with sodium hydroxidesolution as in Method 2. 16.8 gms. of boric acid are next added. 35 gms.of propylene oxide are then added to the suspension and the mixturestirred at 60 C. for 6 hours. The reaction mixture is cooled andfiltered to give 29 gms. of 4-nitr0- toluene 2 (2'-hydroxy-n-propylsulphone. M.P. 99- 101 C.

51.4 parts of 4-nitro-toluene-2-(2'-hydroxy-n-propyl)- sulphone, 25parts of benzaldehyde and 7 parts of piperidine are heated together at140 C. for 6 hours. The reaction mixture is then cooled and 200 parts ofethanol are added to the mixture. The mixture is washed and filtered andwashed with alcohol. The solid so obtained is4-nitro-stilbene-2-(2'-hydroxy-n-propyl)- sulphone, and which has anM.P. of 197 C.

EXAMPLE 3 27.5 parts of4-nitro-toluene-2-(,6,'y-dihydroxy-propyl)-sulphone, 12.5 partsbenzaldehyde and 3.5 parts of piperidine are heated together at 130-140C. for 6 hours. parts of ethanol are added to the cooled reactionmixture and the mixture boiled on a water bath until the product isgranular. The mixture is filtered cold and the solid washed with alittle alcohol. The 4-nitrostilbene-2-(fly-dihydroxypropyl)-sulphonethus obtained has a melting point of 188 C. The 4-nitro-toluene-Z-(flgy-dihydroxypropyl)-sulphone used as starting material can beprepared in the following manner.

Para-nitrotoluene sulphonic acid (sodium salt) (44.6 gms.) and glycidol(14.6 gms.) are heated to 60 C. with good agitation for 6 hours. At theend of the reaction the mixture is cooled, filtered and the4-nitrotoluene-2-(fly-dihydroxypropyl)-sulphone (205 gms.) is obtained,M.P. 94-96 C. On recrystallization from water a product of M.P. 96-98 C.is obtained.

EXAMPLE 4 4-AMINO-STILBENE2- fi-HYDROXY-A ,7 -DIOXA OCTYL)SULPHONE 33.3parts of 4-nitro-toluene-2-(2-hydroxy-4',7'-dioxa octyl)-sulphone, 12.45parts of benzaldehyde and 4 parts of piperidine are heated on an oilbath at 135 C. for 6 hours. The reaction mixture is slurried withmethanol and filtered, and the product is well washed with methanol toyield 4-nitro-stilbene-2-(fi-hydroxy-4,7'-dioxa octyl)- sulphone havinga melting point 142-146" C.

The nitro stilbene is dissolved in polyethylene glycol 300, reduced withiron and aqueous acetic acid and the resultant amino compound basiiiedto Brilliant Yellow by the addition of sodium carbonate. Salt is addedto the reaction mixture, and the solid material filtered 01f andextracted with acetone. The acetone is removed under reduced pressure,and the resulting liquid induced to crystallise. The4-amino-stilbene-2-(2-hydroxy-4,7- dioxa octyl)-sulphone obtained meltsat 95 C.

I claim:

1. A process for producing stilbyl sulphones comprising reacting at anelevated temperature and in the presence of a baisc catalyst ahomocyclic aromatic aldehyde in which the ring structure contains nomore than 10 carbon atoms with a substituted nitrotoluene selected fromthe group consisting of a compound of the formula orn-QNo.

wherein n is an integer from 1410 and R is lower alkyl of from 1 to 4carbon atoms and a compound of the formula where X has the meaning givenabove.

2. A process as claimed in claim 1 wherein said catalyst is a secondaryamine.

3. A compound selected from the group consisting of a compound of theformula wherein n is an integer from 1-10 and R is lower alkyl of from 1to 4 carbon atoms and a compound of the formula OH=OH-X N02 to where X,R and m have the meaning given above.

4. A compound as claimed in claim 3 wherein R is a phenyl group.

5. A process according to claim 1 in which the nitrotoluene sulphone isprepared by reaction of an alkali metal salt of the parent sulphinicacid with an alkylene oxide having at least two carbon atoms.

6. A process according to claim 5 in which the alkylene oxide has notmore than three carbon atoms.

7. A process according to claim 1 in which the nitrottoluene sulphone isprepared by the reaction of an alkali metal salt of the parent sulphinicacid with an alkylene halohydrin having at least two carbon atoms.

8. A process according to claim 7 in which the alkylene halohydrin is analkylene chlorohydrin having not more than three carbon atoms.

9. 4-nitro-stilbene-2-(fit-hydroxyethyl) sulphone.

10. 4-nitro-stilbene-2-(/3,'y-dihydroXypropyl) sulphone.

11. 4-nitro-stilbene 2(2'-hydroxy-n-propyl) sulphone.

12. 4-nitro-stilbene 2-(2 hydroxy-4',7-dioXa-octyl) sulphone.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PROCESS FOR PRODUCING STILBYL SULPHONES COMPRISING REACTING AT ANELEVATED TEMPERATURE AND IN THE PRESENCE OF A BASIC CATALYST AHOMOCYCLIC AROMATIC ALDEHYDE IN WHICH THE RING STRUCTURE CONTAINS NOMORE THAN 10 CARBON ATOMS WITH A SUBSTITUTED NITROTOLUENE SELECTED FROMTHE GROUP CONSISTING OF A COMPOUND OF THE FORMULA
 3. A COMPOUND SELECTEDFROM THE GROUP CONSISTING OF A COMPOUND OF THE FORMULA